Totally agree. Non plug-in series hybrids should be taxed so that plug-in series hybrids are strongly preferred . But not so strong as to make it impossible for folk who have no home or street charging available.What niggles me is the series hybrid is kept quiet about by respected youtubers like fullycharged and transport evolved but as someone who has delighted in driving a BMW i3 94 rex for 2 years now, I know that more plug-in series hybrids available would completely change peoples attitude to ev and substantially increase the miles driven electric.
When you see the difference between a two year old i3 with or without REx can be as little as £700 then another 60 miles of range looks like a very good deal. Contrast the price difference second hand if you wanted to jump the battery range up by another 60 miles in a pure BEV. Dual fuel flexibility goes a long way to offsetting costs with the more complex servicing and higher risk of repairs being needed.
There must be a sweet spot somewhere that offers best value for money between the size of the battery and the robustness of the range extender. More sales should easily generate more EV miles driven than limited sales of pure BEVs thus reducing CO2 emissions sooner.
My i3 94Ah REx has replaced a 24 kWh LEAF and an old petrol ICE. The result is far more miles driven annually without burning fossil fuel (at 159 g CO2 per km) and better utilisation of a battery (embodied CO2 from manufacture) than will decay anyway with time regardless of how quickly it clocks up the miles.
We have to start thinking about each car's lifetime miles per kWh of installed battery achieved if we are going to tame the monster of CO2 emissions.